diff options
Diffstat (limited to 'compiler/cmm/PprC.hs')
| -rw-r--r-- | compiler/cmm/PprC.hs | 30 |
1 files changed, 27 insertions, 3 deletions
diff --git a/compiler/cmm/PprC.hs b/compiler/cmm/PprC.hs index 3b824f375f..68b6bf7445 100644 --- a/compiler/cmm/PprC.hs +++ b/compiler/cmm/PprC.hs @@ -1223,8 +1223,9 @@ commafy xs = hsep $ punctuate comma xs pprHexVal :: Integer -> Width -> SDoc pprHexVal 0 _ = ptext (sLit "0x0") pprHexVal w rep - | w < 0 = parens (char '-' <> ptext (sLit "0x") <> go (-w) <> repsuffix rep) - | otherwise = ptext (sLit "0x") <> go w <> repsuffix rep + | w < 0 = parens (char '-' <> + ptext (sLit "0x") <> intToDoc (-w) <> repsuffix rep) + | otherwise = ptext (sLit "0x") <> intToDoc w <> repsuffix rep where -- type suffix for literals: -- Integer literals are unsigned in Cmm/C. We explicitly cast to @@ -1239,10 +1240,33 @@ pprHexVal w rep else panic "pprHexVal: Can't find a 64-bit type" repsuffix _ = char 'U' + intToDoc :: Integer -> SDoc + intToDoc i = go (truncInt i) + + -- We need to truncate value as Cmm backend does not drop + -- redundant bits to ease handling of negative values. + -- Thus the following Cmm code on 64-bit arch, like amd64: + -- CInt v; + -- v = {something}; + -- if (v == %lobits32(-1)) { ... + -- leads to the following C code: + -- StgWord64 v = (StgWord32)({something}); + -- if (v == 0xFFFFffffFFFFffffU) { ... + -- Such code is incorrect as it promotes both operands to StgWord64 + -- and the whole condition is always false. + truncInt :: Integer -> Integer + truncInt i = + case rep of + W8 -> i `rem` (2^(8 :: Int)) + W16 -> i `rem` (2^(16 :: Int)) + W32 -> i `rem` (2^(32 :: Int)) + W64 -> i `rem` (2^(64 :: Int)) + _ -> panic ("pprHexVal/truncInt: C backend can't encode " + ++ show rep ++ " literals") + go 0 = empty go w' = go q <> dig where (q,r) = w' `quotRem` 16 dig | r < 10 = char (chr (fromInteger r + ord '0')) | otherwise = char (chr (fromInteger r - 10 + ord 'a')) - |